1. Field of the Invention
The present invention relates to a transfer assembly comprising an intracorporeal transfer coil of an implant and an extracorporeal transfer coil of an extracorporeal supply means.
2. Description of Related Art
Medical implants for supporting the heart and organ activities, for example, can generally be partially or fully implanted. Partially implanted implants comprise lines for energy supply and data transfer, said lines extending through the skin to an extracorporeal transfer means. The line lead-through devices in the skin are a common source of infection. Further, the patient is restricted in his freedom of movement by the line lead-through devices.
As an alternative to partially implanted implants, fully implanted implants are provided. In particular implants performing mechanical work, for example blood pumps, have an energy requirement of 2 to 20 watts. This required energy can be made available by the implant's own accumulator for a short period of a few hours at the most. For operating implants with an energy requirement of more than 1 to 2 watts, a continuous or nearly continuous extracorporeal energy supply is indispensable. The energy supply of such an implant and the data transfer are carried out in a cordless manner through an intracorporeal supply coil of the implant and an extracorporeal transfer coil of the supply means. Energy and data are inductively transferred between the two transfer coils. For data and energy transfer between the supply means and the implant, the two transfer coils are placed one on top of the other such that they overlap each other to the largest extent possible. The extracorporeal supply means is frequently configured as a belt or a pouch and extracts the energy to be transferred to the implant from batteries or the public power supply system.
For obtaining as high an efficiency as possible during energy and data transfer, the two transfer coils must be placed one on top of the other as exactly as possible and must then be correspondingly fixed relative to each other. Said fixing is carried out by gluing the supply means and/or its transfer coil to the skin, for example.
Transfer assemblies are known which are comfortable to be used by a patient and whose supply means and/or transfer coil are not fixed by gluing. For example, the transfer coil of the supply means may be accommodated in a belt which can be easily removed by the patient. However, since the transfer coil of the supply means is not fixed to the skin by gluing, there is the risk that, during the inductive transfer, the belt and the transfer coil of the supply means shift when the patient moves, and therefore the electromagnetic coupling and thus the efficiency of the energy transfer and the data transfer are reduced.
Another problem is the exact placing and alignment of the extracorporeal transfer coil of the supply means over or on top of the intracorporeal transfer coil of the implant. In practice, the position of the intracorporeal transfer coil of the implant must be located by palpating. If it is not possible to locate the transfer coil of the implant by palpating, a corresponding marking is to be placed at the respective place on the skin of the patient.
In US 2004/0106963 A1 a transfer assembly for an implant is described, where on the implant side a ferromagnetic tissue mat and, alternatively, a mat comprising a plurality of microchips is provided. The signals from the ferromagnetic mat cannot be modulated. Further, a direction of offset cannot be clearly determined from the point of view of the supply means. Although the alternative implant-side mat made of microchips theoretically allows a direction of offset to be determined, said direction of offset can be determined only from the point of view of the implant. A correction indication could therefore only be supplied from the implant side. Indication of the direction of offset at the extracorporeal supply means would require knowledge of the rotatory position of the supply means.
From the printed publication WO 2004/021876 A1 a transfer assembly is known which comprises a single coil both at the implant side and at an extracorporeal location for determining the amount of offset.